Ethoxycarbonylmethylene phosphorane

Selective epoxidation of the isolated double bond (Equation 35) in the ester 79, prepared from citronellal and triphenyl(ethoxycarbonylmethylene)phosphorane, followed by treatment with Na2PdCl4 and v/-butyl hydroperoxide gives the bis-ether 80 <1994CC903>. 

The dione (100) reacted exclusively at the exocyclic carbonyl in a synthesis of methyl 9-cis- (101) and 9-rra/i5 -trisporates B. Although ( )-dihydro-j8-santalol (103) was obtained from (102) in 90% yield if the hydroxy-group was protected as the borate ester, use of unprotected (102) gave predominantly the isomeric olefin (104). Similarly the hydroxy-ketone (105) gave the olefin (106), but similar rearrangements did not occur using the isopropylidene- or ethoxycarbonylmethylene-phosphoranes. 

Ethyl (triphenylphosphoranylidene)acetate is available from FIuka AG and Trldom Chemical Inc. under the name (ethoxycarbonylmethylene)triphenyl-phosphorane and from Aldrich Chemical Company, Inc. under the name (carbethoxymethylene)triphenylphosphorane. The reagent may be prepared from triphenyl phosphine and ethyl bromoacetate by the following procedure. ... 

Methylmaleinimide was prepared from citraconic anhydride and methylammonium acetate and after reaction with ethoxycarbonylmethylene(triphenyl)phosphorane (CMTP) gave ( )-5-ylidenepyrrol-2-(5//)-one (A) regio- and stereoselectively [160] (Scheme 39). 

In guten Ausbeuten verlauflt jedoch die Wittig-Reaktion von 2-Benzyloxy-6-hydroxy-4-methoxy-acctophenon mit (Ethoxycarbonylmethylen)-triphenyl-phosphoran zum 5-Benzyloxy-7-methoxy-4-methyl-Cumarin (72%)373 374 ... 

Wittig Alkenation Reactions. The tosyhnethylene phosphorane is classified as a stabilized Wittig reagent because of the extra negative charge stabilization by the sulfone substituent on the yUdic carbon. Other stabilized ylides include (methoxy-or ethoxycarbonylmethylene)triphenylphosphorane, cyano-... 

The phosphonium salt (280) is formed on treatment of ethoxycarbonylmethylene-triphenylphosphorane with phenyl-lithium and methyl iodide. The keten (281), formed by elimination of ethanol from the phosphorane, is suggested as a likely intermediate. 

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